This condition occurs when not enough thyroid hormones are produced. Since the thyroid hormones affect many systems
in the body, including metabolic regulation, a variety of symptoms are produced. Most common are lethargy, weight gain,
hair loss, and skin problems.
The thyroid glands located in the neck produce hormones
that affect the function of many parts of the body. Although thyroid disease in cats often causes over productive glands and
too much hormone, dogs with thyroid disease usually have a low production of thyroid hormones.
Overactive
thyroid glands in the dog are rare and are usually associated with cancer. Hypothyroidism in dogs is usually caused by inflammation
or shrinkage of the thyroid gland. Thyroid cancer can cause hypothyroidism although it does not occur commonly in dogs. Hypothyroidism
occurs more commonly in medium to large breed dogs and usually in middle aged dogs. Breeds most commonly affected include: Golden
retriever, Doberman pincher, and the Irish setter.
Symptoms
The most common signs of low thyroid function in dogs include loss or thinning of the fur, dull hair coat, excess shedding
or scaling, weight gain, reduced activity and reduced ability to tolerate the cold. The hair loss occurs primarily over the
body, sparing the head and legs, and is usually not accompanied by itching or redness of the skin. Some dogs will have thickening
of the skin and increased skin pigment, especially in areas of friction, such as the armpit (axilla). Hypothyroid dogs often
have ear infections and show ear pain, redness, and odor. Hypothyroid dogs may also develop skin infections which may be itchy
and result in sores on the body. The accumulation of substances called mucopolysaccharides can cause the muscles of the face
to droop giving the dog a facial expression that is sometimes called "tragic".
Less commonly
recognized signs that may be seen in a small number of dogs with hypothyroidism include dilation of the esophagus (megaesophagus)
causing regurgitation, and abnormal function of nerves or muscles leading to weakness or abnormal ability to walk.
Diagnosis
The condition is identified by a blood test that checks the level of thyroid hormones: baseline T4, Baseline T3, Free T4,
and TSH. Often, a TSH stimulation test is also performed. Dogs may have a mild anemia and increased levels of cholesterol.
There are several blood tests that can be used to confirm a suspected diagnosis of hypothyroidism. Blood testing
for hypothyroidism is often performed as a panel of several tests in order to increase the yield of these tests. The results
of some of these tests can be influenced by the presence of other non-thyroid diseases, so test results must be considered
in light of the whole picture.
Treatment
Treatment of hypothyroidism is by giving oral replacement
hormone for the rest of the dog's life. Initially thyroid hormone is usually given twice daily. Once the hair coat begins
to improve, some dogs can be maintained on once daily medication. There are two general forms of thyroid medication, T3 and
T4. T4 is converted to T3 by the body. Most hypothyroid dogs given T4 will convert it to T3 so almost all hypothyroid dogs
receive T4 (levothyroxine or L-thyroxine). A few dogs are unable to make this conversion and require T3 medication.
It
usually takes 4 to 6 weeks before regrowth of the fur is apparent. In dogs with associated ear infection, the ears should
be cleaned and treated with antibiotics either in the ear or by mouth. Blood levels of the T4 are often measured in order
to fine tune the dose.
This information comes from the Veterinary College at Washington State University. They
assume no liability for injury to you or your pet incurred by following these descriptions or procedures.
We
are looking for blood samples from Airedales affected with hypothryoidism. Contact
[email protected]
for more information.
Resources from Veterinarians and Research Scientists
studying Hypothyroidism in canines:
By Raymond A. Weitkamp, D.V.M.
G. Greg Keller, D.V.M., M.S., Dipl. ACVR
Ray Nachreiner, D.V.M.,
Ph.D.
http://www.pbgv.org/images/Health/Dr-Roughie-ST-Column/Jun05Hypothyriodism.pdf
